The measure is one of several points of friction between Steinberg and the unions, especially the powerful California Teachers Association, which has used billboards and mailings to criticize the Democratic head of the Senate.

Steinberg's Senate Bill 1285 was approved by the Assembly Education Committee on a 6-2 vote after a lengthy hearing. It's aimed at modifying the long-standing seniority system that, Steinberg and his allies say, creates high turnover and uncertainty in low-performing schools with high numbers of poor and nonwhite students.

"It's about civil rights," Steinberg told the committee.

The measure would generally prohibit staff changes at low-performing schools that are disproportionate to those in school districts as a whole, responding to civil rights lawsuits that contend poor youngsters are being damaged by discriminatory allocation of teachers and other resources.

The unions contend, among other things, that the legislation would rely on state-administered tests that categorize school performance scores, which smacks of using test scores for teacher evaluation, a long-standing policy controversy.

The Education Committee was the measure's first test because its provisions were inserted after it had cleared the Senate. It still faces a series of committee and floor votes where the union opposition could be decisive.

Assemblyman Tom Torlakson, D-Pittsburg, was one of the two Democratic Assembly members to vote against the bill. He is the union-backed candidate running for state superintendent of schools in November.